cmd/link,cmd/internal/obj/riscv: add TLS support for linux/riscv64

Add support for Thread Local Storage (TLS) for linux/riscv64 with external
linking, using the initial-exec model.

Update #36641

Change-Id: I3106ef9a29cde73215830b00deff43dbec1c76e0
Reviewed-on: https://go-review.googlesource.com/c/go/+/263478
Trust: Joel Sing <joel@sing.id.au>
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

4 files changed, 44 insertions, 12 deletions

diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 7bd3984e51..da49f67138 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -1984,6 +1984,13 @@ func assemble(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				ctxt.Diag("AUIPC needing PC-relative reloc missing symbol")
 				break
 			}
+			if addr.Sym.Type == objabi.STLSBSS {
+				if rt == objabi.R_RISCV_PCREL_ITYPE {
+					rt = objabi.R_RISCV_TLS_IE_ITYPE
+				} else if rt == objabi.R_RISCV_PCREL_STYPE {
+					rt = objabi.R_RISCV_TLS_IE_STYPE
+				}
+			}
 
 			rel := obj.Addrel(cursym)
 			rel.Off = int32(p.Pc)
diff --git a/src/cmd/internal/objabi/reloctype.go b/src/cmd/internal/objabi/reloctype.go
index 9e2e4a150a..938954e07a 100644
--- a/src/cmd/internal/objabi/reloctype.go
+++ b/src/cmd/internal/objabi/reloctype.go
@@ -223,6 +223,14 @@ const (
 	// AUIPC + S-type instruction pair.
 	R_RISCV_PCREL_STYPE
 
+	// R_RISCV_TLS_IE_ITYPE resolves a 32-bit TLS initial-exec TOC offset
+	// address using an AUIPC + I-type instruction pair.
+	R_RISCV_TLS_IE_ITYPE
+
+	// R_RISCV_TLS_IE_STYPE resolves a 32-bit TLS initial-exec TOC offset
+	// address using an AUIPC + S-type instruction pair.
+	R_RISCV_TLS_IE_STYPE
+
 	// R_PCRELDBL relocates s390x 2-byte aligned PC-relative addresses.
 	// TODO(mundaym): remove once variants can be serialized - see issue 14218.
 	R_PCRELDBL
diff --git a/src/cmd/internal/objabi/reloctype_string.go b/src/cmd/internal/objabi/reloctype_string.go
index 01df4cce62..693d9631f5 100644
--- a/src/cmd/internal/objabi/reloctype_string.go
+++ b/src/cmd/internal/objabi/reloctype_string.go
@@ -59,17 +59,19 @@ func _() {
 	_ = x[R_ADDRPOWER_TOCREL_DS-49]
 	_ = x[R_RISCV_PCREL_ITYPE-50]
 	_ = x[R_RISCV_PCREL_STYPE-51]
-	_ = x[R_PCRELDBL-52]
-	_ = x[R_ADDRMIPSU-53]
-	_ = x[R_ADDRMIPSTLS-54]
-	_ = x[R_ADDRCUOFF-55]
-	_ = x[R_WASMIMPORT-56]
-	_ = x[R_XCOFFREF-57]
+	_ = x[R_RISCV_TLS_IE_ITYPE-52]
+	_ = x[R_RISCV_TLS_IE_STYPE-53]
+	_ = x[R_PCRELDBL-54]
+	_ = x[R_ADDRMIPSU-55]
+	_ = x[R_ADDRMIPSTLS-56]
+	_ = x[R_ADDRCUOFF-57]
+	_ = x[R_WASMIMPORT-58]
+	_ = x[R_XCOFFREF-59]
 }
 
-const _RelocType_name = "R_ADDRR_ADDRPOWERR_ADDRARM64R_ADDRMIPSR_ADDROFFR_WEAKADDROFFR_SIZER_CALLR_CALLARMR_CALLARM64R_CALLINDR_CALLPOWERR_CALLMIPSR_CALLRISCVR_CONSTR_PCRELR_TLS_LER_TLS_IER_GOTOFFR_PLT0R_PLT1R_PLT2R_USEFIELDR_USETYPER_USEIFACER_USEIFACEMETHODR_METHODOFFR_POWER_TOCR_GOTPCRELR_JMPMIPSR_DWARFSECREFR_DWARFFILEREFR_ARM64_TLS_LER_ARM64_TLS_IER_ARM64_GOTPCRELR_ARM64_GOTR_ARM64_PCRELR_ARM64_LDST8R_ARM64_LDST32R_ARM64_LDST64R_ARM64_LDST128R_POWER_TLS_LER_POWER_TLS_IER_POWER_TLSR_ADDRPOWER_DSR_ADDRPOWER_GOTR_ADDRPOWER_PCRELR_ADDRPOWER_TOCRELR_ADDRPOWER_TOCREL_DSR_RISCV_PCREL_ITYPER_RISCV_PCREL_STYPER_PCRELDBLR_ADDRMIPSUR_ADDRMIPSTLSR_ADDRCUOFFR_WASMIMPORTR_XCOFFREF"
+const _RelocType_name = "R_ADDRR_ADDRPOWERR_ADDRARM64R_ADDRMIPSR_ADDROFFR_WEAKADDROFFR_SIZER_CALLR_CALLARMR_CALLARM64R_CALLINDR_CALLPOWERR_CALLMIPSR_CALLRISCVR_CONSTR_PCRELR_TLS_LER_TLS_IER_GOTOFFR_PLT0R_PLT1R_PLT2R_USEFIELDR_USETYPER_USEIFACER_USEIFACEMETHODR_METHODOFFR_POWER_TOCR_GOTPCRELR_JMPMIPSR_DWARFSECREFR_DWARFFILEREFR_ARM64_TLS_LER_ARM64_TLS_IER_ARM64_GOTPCRELR_ARM64_GOTR_ARM64_PCRELR_ARM64_LDST8R_ARM64_LDST32R_ARM64_LDST64R_ARM64_LDST128R_POWER_TLS_LER_POWER_TLS_IER_POWER_TLSR_ADDRPOWER_DSR_ADDRPOWER_GOTR_ADDRPOWER_PCRELR_ADDRPOWER_TOCRELR_ADDRPOWER_TOCREL_DSR_RISCV_PCREL_ITYPER_RISCV_PCREL_STYPER_RISCV_TLS_IE_ITYPER_RISCV_TLS_IE_STYPER_PCRELDBLR_ADDRMIPSUR_ADDRMIPSTLSR_ADDRCUOFFR_WASMIMPORTR_XCOFFREF"
 
-var _RelocType_index = [...]uint16{0, 6, 17, 28, 38, 47, 60, 66, 72, 81, 92, 101, 112, 122, 133, 140, 147, 155, 163, 171, 177, 183, 189, 199, 208, 218, 234, 245, 256, 266, 275, 288, 302, 316, 330, 346, 357, 370, 383, 397, 411, 426, 440, 454, 465, 479, 494, 511, 529, 550, 569, 588, 598, 609, 622, 633, 645, 655}
+var _RelocType_index = [...]uint16{0, 6, 17, 28, 38, 47, 60, 66, 72, 81, 92, 101, 112, 122, 133, 140, 147, 155, 163, 171, 177, 183, 189, 199, 208, 218, 234, 245, 256, 266, 275, 288, 302, 316, 330, 346, 357, 370, 383, 397, 411, 426, 440, 454, 465, 479, 494, 511, 529, 550, 569, 588, 608, 628, 638, 649, 662, 673, 685, 695}
 
 func (i RelocType) String() string {
 	i -= 1
diff --git a/src/cmd/link/internal/riscv64/asm.go b/src/cmd/link/internal/riscv64/asm.go
index 66c47c69f8..c18e0540d8 100644
--- a/src/cmd/link/internal/riscv64/asm.go
+++ b/src/cmd/link/internal/riscv64/asm.go
@@ -38,7 +38,8 @@ func genSymsLate(ctxt *ld.Link, ldr *loader.Loader) {
 		relocs := ldr.Relocs(s)
 		for ri := 0; ri < relocs.Count(); ri++ {
 			r := relocs.At(ri)
-			if r.Type() != objabi.R_RISCV_PCREL_ITYPE && r.Type() != objabi.R_RISCV_PCREL_STYPE {
+			if r.Type() != objabi.R_RISCV_PCREL_ITYPE && r.Type() != objabi.R_RISCV_PCREL_STYPE &&
+				r.Type() != objabi.R_RISCV_TLS_IE_ITYPE && r.Type() != objabi.R_RISCV_TLS_IE_STYPE {
 				continue
 			}
 			if r.Off() == 0 && ldr.SymType(s) == sym.STEXT {
@@ -100,7 +101,7 @@ func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 		// TODO(jsing): Consider generating elf.R_RISCV_CALL instead of a
 		// HI20/LO12_I pair.
 
-	case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
+	case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE, objabi.R_RISCV_TLS_IE_ITYPE, objabi.R_RISCV_TLS_IE_STYPE:
 		// Find the text symbol for the AUIPC instruction targeted
 		// by this relocation.
 		relocs := ldr.Relocs(s)
@@ -126,6 +127,10 @@ func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 			hiRel, loRel = elf.R_RISCV_PCREL_HI20, elf.R_RISCV_PCREL_LO12_I
 		case objabi.R_RISCV_PCREL_STYPE:
 			hiRel, loRel = elf.R_RISCV_PCREL_HI20, elf.R_RISCV_PCREL_LO12_S
+		case objabi.R_RISCV_TLS_IE_ITYPE:
+			hiRel, loRel = elf.R_RISCV_TLS_GOT_HI20, elf.R_RISCV_PCREL_LO12_I
+		case objabi.R_RISCV_TLS_IE_STYPE:
+			hiRel, loRel = elf.R_RISCV_TLS_GOT_HI20, elf.R_RISCV_PCREL_LO12_S
 		}
 		out.Write64(uint64(sectoff))
 		out.Write64(uint64(hiRel) | uint64(elfsym)<<32)
@@ -156,7 +161,7 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
 		case objabi.R_CALLRISCV:
 			return val, 0, true
 
-		case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
+		case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE, objabi.R_RISCV_TLS_IE_ITYPE, objabi.R_RISCV_TLS_IE_STYPE:
 			return val, 2, true
 		}
 
@@ -170,6 +175,16 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
 		// Nothing to do.
 		return val, 0, true
 
+	case objabi.R_RISCV_TLS_IE_ITYPE, objabi.R_RISCV_TLS_IE_STYPE:
+		// TLS relocations are not currently handled for internal linking.
+		// For now, TLS is only used when cgo is in use and cgo currently
+		// requires external linking. However, we need to accept these
+		// relocations so that code containing TLS variables will link,
+		// even when they're not being used. For now, replace these
+		// instructions with EBREAK to detect accidental use.
+		const ebreakIns = 0x00100073
+		return ebreakIns<<32 | ebreakIns, 0, true
+
 	case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
 		pc := ldr.SymValue(s) + int64(r.Off())
 		off := ldr.SymValue(rs) + r.Add() - pc
@@ -222,7 +237,7 @@ func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc, sym.RelocVariant
 
 func extreloc(target *ld.Target, ldr *loader.Loader, r loader.Reloc, s loader.Sym) (loader.ExtReloc, bool) {
 	switch r.Type() {
-	case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE:
+	case objabi.R_RISCV_PCREL_ITYPE, objabi.R_RISCV_PCREL_STYPE, objabi.R_RISCV_TLS_IE_ITYPE, objabi.R_RISCV_TLS_IE_STYPE:
 		return ld.ExtrelocViaOuterSym(ldr, r, s), true
 	}
 	return loader.ExtReloc{}, false